Looking at their website, I see they do have some "bear incidents" but it certainly doesn't seem to be such an issue.
My guess is our problem is from past behavior...of humans. Looking at old Yosemite photos and movies, you see how uttterly stupid people have been in the past. They had a big garbage dump where it was a nightly event to go watch the bears get fed the restaurant garbage (no doubt just prior to watching them push a bonfire over Glacier point to provide a "pretty" firefall 8^( )
Bears are extremely intelligent, and not only learn new things (there was one in Yosemite that had learned to open car doors...not by the usual window-pry, but with the handle) and they pass this along to other bears and offspring. They could have easily distributed themselves over a large part of California, along with their behavior, in this amount of time.
So I'd guess the bear problem is something that foolish behavior of our predecessors has left us to "enjoy". In distant places, where this foolish human behavior hasn't happened, there would be fewer problems. Just a guess.
If you've ever watched a black bear scratch through a rotten tree for termites etc., you can understand why an ice chest full of human food looks so attractive 8^).